In the conventional toothed belt drive system, a flexible toothed belt is engaged with a pulley in complementary radially outwardly opening grooves thereof. A problem arises in such belt drives in that noise is produced by the belt teeth as they engage and disengage from the pulley during the operation of the drive.
One conventional form of toothed drive system utilizes pulley teeth having a trapezoidal cross section and complementary trapezoidal cross section pulley grooves.
A number of other tooth-and-pulley groove configurations have been utilized in an effort to abate the vexatious noise problem, but none has proven completely successful.